A recent study has shown that the ancient dunes preserved in the rock record of Gale crater migrated across the surface of Mars in the opposite direction to the dunes active on the surface today. The ancient dunes, known as the Stimson formation, were analyzed by the NASA Mars Science Laboratory’s (MSL) Curiosity rover at two locations using the Chemistry and Camera (ChemCam) instrument suite. ChemCam fires a laser at the martian surface creating plasma, which emits wavelengths of light characteristic of the chemical elements present in the target. A team led by Candice Bedford at the Lunar and Planetary Institute identified chemical trends indicative of changes in mineralogy across the Stimson formation. These changes in mineralogy suggest that the ancient dunes migrated across the surface of Mars after the environment changed from one that could support a perennial river-lake system to the cold, arid climate observed today. These chemical trends also suggest a southwest-northeast wind direction, which is opposite of that determined for the active Bagnold dunes, and thus implies a change in the wind regime with time. A change in sediment transport direction between the ancient and modern dunes in Gale crater complements geochemical and mineralogical evidence for different sediment source regions. READ MORE